In vehicle engines, a crankshaft is supported in a lower part of a cylinder block by a crankshaft supporter as shown in FIGS. 11 and 12. FIG. 11 shows an engine 102, a cylinder block 104, a crankshaft 106, and a crankshaft supporter 108. The crankshaft supporter 108 includes, in the cylinder block 104, a bearing section 110, mounting sections 112 adjacent the sides of the bearing 110, and outer walls 114 outward of the mounting sections 112.
The bearing section 110 in the cylinder block includes a bearing metal 116. The mounting sections 112 in the cylinder block have bolt screw holes 120 which are opened to a mounting surface 118 of the cylinder block. As shown in FIG. 12, the mounting surface 118 defines therein a knock-pin (dowel) hole 122 that opens to the mounting surface 118 and in coaxial alignment with the bolt screw holes 120.
The crankshaft supporter 108 is mounted to the cylinder block 104 of the engine 102 so as to support the crankshaft 106, and includes a lower crankcase 128 that is formed of aluminum alloy as a matrix 124 and that has a preform (core material) 126 cast (embedded) therein.
The lower crankcase 128 is provided with a bearing section 130 opposed to the bearing section 110 in the cylinder block, mounting sections 132 located adjacent both sides of the bearing section 130 and attached to the mounting sections 112 in the cylinder block, and outer walls 134 outward of the mounting sections 132 to correspond to the outer walls 114 in the cylinder block.
The bearing section 130 in the lower crankcase is equipped with a bearing metal 136 corresponding to the bearing metal 116 in the cylinder block. The mounting sections 132 in the lower crankcase include bolt holes 140 which correspond to the bolt holes 120 and which are opened to a mounting surface 138 of the lower crankcase. A dowel hole 142 opened to the mounting surface 138 is defined in coaxial alignment with the bolt hole 140.
The preform 126 includes a support section 144 that is cast in the bearing section 130, and penetrated sections 146 adjacent both sides of the support section 144 to be cast in the mounting section 132 in the lower crankcase. The penetrated sections 146 include opposing surfaces 148 facing toward the mounting surface 132 in the lower crankcase, and through holes 150 which define the bolt holes 140. The preform 126 is formed by firing alumina fibers, and the matrix 124 of aluminum alloy penetrates the preform during casting to form a fiber-reinforced metal (FRM) section 152.
In the crankshaft supporter 108, the crankshaft 106 is disposed between the bearing metals 116, 136, and is aligned by inserting a dowel sleeve 154 into the dowel holes 122, 142. By threadedly inserting coupling bolts 156 through the holes 140 and dowel sleeves 154 into the bolt screw holes 120 while contacting the mounting surfaces 118, 138 with each other, the lower crankcase 128 is fixedly mounted to the cylinder block 104 so as to support the crankshaft 106 therebetween. An oil pan (not shown) is mounted to a bottom of the lower crankcase 128.
A crankshaft supporter as disclosed in JP 2000-337348 includes a supporting structure to support a crankshaft in an internal combustion engine, and a holding section to support the support structure, wherein the supporting structure is made of porous material, and material of the holding section flows into pores in the supporting structure.
According to a crankshaft supporter disclosed in JP 2001-71117, a cylindrical preform having a certain volume is set in a cavity in a mold, and molten metal is poured into the cavity so as to cast a cylinder block with the preform embedded therein. The preform has a part, on a side where the molten metal is poured, that is more rigid than the other part.
A crankshaft supporter disclosed in JP 2002-61538 includes: a main body of a cylinder block; a bearing below the main body; a crankshaft rotatably supported by bearing sections that are formed in a lower part of the main body and in a bearing section; aluminum alloy layer in a sliding section of the bearing section; and a composite material around the layer having a lower coefficient of thermal expansion than that of the layer in the sliding section.
In the conventional crankshaft supporter 108 shown in FIGS. 11 and 12, the cylinder block 104 and the lower crankcase 128 are positioned by inserting the dowel 154 into the dowel holes 122, 142 formed in the cylinder block 104 and the lower crankcase 128. When the lower crankcase 128 has the preform 126 cast within the matrix 124 of aluminum alloy, the dowel holes 142 need to be subjected to a cutting process so as to be opened to the mounting surface 134 of the lower case after casting.
At this time, as shown in FIG. 12, not only the matrix 124 but also the FRM section 152 in the lower crankcase 128 needs to be cut after casting to a depth “b” for the dowel, as measured from the mounting surface 138, to form the dowel hole 142 in the lower crankcase. This depth “b” is greater than depth “a” of the matrix, as measured from the mounting surface 138 of the lower crankcase to the opposing surface 148 of the penetrated section 146 of the preform 126. However, the FRM section 152 is rigid (i.e. hard) due to the matrix 124 of aluminum alloy which has penetrated into the preform 126 during casting. The dowel hole 142 is formed by cutting the FRM section 152 that is more rigid (i.e. hard) than the matrix 124 of aluminum alloy after the casting process, which cutting is hard to process and severely wears the blades of the cutting tools.
In order to obviate or minimize the above-mentioned inconvenience, the present invention provides a crankshaft supporter having a support member which is attached to a cylinder block of an engine so as to support a crankshaft and which is formed of a matrix of aluminum alloy with a preform cast inside. The support member includes a mounting surface in contact with a mounting surface on the cylinder block, a bolt hole corresponded to a bolt hole in the cylinder block and opened to the mounting surface of the support member, and a dowel hole in coaxial alignment with the bolt hole and opened to the mounting surface of the support member. In the crankshaft supporter, a penetrated section is formed in the preform and a through hole defining the bolt hole is formed therein, and a recessed section formed of the matrix to shape the dowel hole is positioned between the mounting surface of the support member and an opposing surface of the penetrated section that faces the mounting surface.
According to the present invention, due to the recessed section for shaping the dowel hole made of the matrix and positioned between the mounting surface of the support member and an opposing surface of the penetrated section, only the matrix of aluminum alloy must be cut to permit forming of the dowel hole after casting, which eliminates cutting of the FRM section that is more hard than the aluminum alloy matrix.